The experimental material is barley, which accounts for a large share in the formulations of dry compound feed. The size reduction was performed in each case with a laboratory roller mill “QC-109 Pionier” of the company “Labor” MIM Budapest (Hungaria) and a laboratory hammer mill “RECORD A” of the company Jemlich (Germany). The dry matter content was a uniform DM = 85.5%. In order to be able to determine the influence of the particle size, after grinding samples with the following size fractions were produced with the help of a flat screening machine: 315 μm > x > 250 μm 250 μm > x > 200 μm 200 μm > x > 160 μm 160 μm > x > 100 μm All the samples lie in the fine-grain size range. This was intentional because even slight shares of cohesive fines affect the flow behaviour of the entire material system (Fürll, 2007; Fürll and Hoffmann, 2012; Fürll and Hoffmann, 2013). Above all, the physical properties of the fine material are of interest